skip to content

Darwin Correspondence Project

From E. W. Black   13 August 1877

East Riverside, Fayette Co., Pa | U.S.A.

August 13th. ’77.

Mr. Charles Darwin, F. R. S.,

Respected Sir:

enclosed please find specimens of flowers of the common American milk-weed, (Asclepias Syriaca) with entrapped insects, which may be of interest to you on account of its bearing on the habits of plants in regard to fertilization, and hence on the theory of Evolution.1 As you will observe, the insects are of different species—although, from the lateness of the season, my specimens are rather meagre—and I have repeatedly seen many kinds not herein represented hanging dead to the flowers of this plant, and among them even the ingenious and comparatively stout hive-bee. (Apis Mellifica)2 The Bitter-Root or Jordian Hemp, a plant with closely similar flowers, has the same habit though it appears less successful in affecting a capture, as the victims are far more rare than in the case of the former plant.3 They are both quite common here, abounding in moist places in both high- and lowlands. Should you desire to communicate in regard to anything in this part of the world I will be happy to inform you on any subject of which I may have any knowledge.

Hoping to hear from you soon in regard to the bearing of the specimens on the above theory, etc., I remain, | Your Obedient Servt., | E. Willson Black.

Footnotes

In Origin, p. 193, CD had noted that flowers of Asclepias had pollen-grains held together on pollinia. The structure of the flower is such that an insect with pollinia attached to its legs can easily be trapped in one of the narrow slits of the stigmatic chambers.
Apis mellifica is a synonym of A. mellifera (European honey-bee).
Jordan hemp and bitter-root are alternative common names for Apocynum androsaemifolium (fly-trap dogbane); CD was interested in discovering the mechanism by which it trapped insects (see letter to D. F. Nevill, 15 January 1877 and n. 1).

Bibliography

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

Summary

Encloses specimens of milk-weed with trapped insects. Indian hemp catches insects in the same way but with less success.

Letter details

Letter no.
DCP-LETT-11104
From
Evans Willson Black
To
Charles Robert Darwin
Sent from
Fayette County, Pa.
Source of text
DAR 160: 190
Physical description
ALS 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 11104,” accessed on 24 April 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-11104.xml

letter